In view of the limited reserves of oil of oil-importing nations, such as the United States, and the ever increasing cost of importing this presently essential fuel source, a need has arisen for new rechargeable battery systems which are high in both specific energy and specific power, and which, for example, could be used in the transportation field to propel automobiles and other vehicles. By use of such batteries, transportation energy use could be shifted, at least in part, from imported oil to coal and nuclear energy. Such battery systems might also be used by the utility industry for storing electric power and using it in periods of peak demand to smooth the generating load, so that the need for burning petroleum fuels for the generation of peaking power is reduced.
A promising battery for the above-stated purpose is an uncharged cell, the positive and negative electrodes of which are prepared from a mixture of iron powder and lithium sulfide (Li.sub.2 S) for the positive electrode and a porous aluminum plaque for the negative electrode. Upon charging, the lithium in the positive electrode is electro-chemically transferred to the negative electrode, forming a lithium-aluminum alloy, and in the positive electrode the sulfur from the Li.sub.2 S forms FeS or FeS.sub.2 depending upon the cell charging voltage.
In preparing batteries of this type it is essential that the Li.sub.2 S be of extremely high purity and be in the form of a finely divided flowable powder whereby it can be intimately and uniformly mixed with the iron powder.
Various processes have been suggested for production of high purity lithium sulfide. These include reaction of lithium ethoxide and hydrogen sulfide; lithium metal with hydrogen sulfide in organic solvents such as diethyl ether or tetrahydrofuran; lithium sulfate with hydrogen, and lithium metal with sulfur in the presence or absence of a solvent. These several processes have one or more drawbacks, such as slow reaction rate, impure product and cost. Reactions run in organic solvents have the disadvantage in that complete solvent removal is difficult, and poor filtration characteristics frequently make the processes impractical and costly.